1. Field of the Invention
The present invention relates to downhole lubricants and spotting fluids. More particularly, the present invention relates to the use of a synthetic hydrocarbon compound, in particular polyalphalolefin delivered downhole as a lubricant having improved performance and lower toxicity levels than other non-synthetic oil based fluids, used particularly for preventing sticking of the drill bit, or as a spotting fluid for dislodging a bit lodged in the formation.
2. General Background
In the drilling of oil wells, wherein a drill bit at the end of a rotating drill string, or at the end of a motor drill, it is very common that as the bit is rotated through the formation for the drilling of the well, that at certain depths in the formation, the drill bit may have a tendency to become lodged within the formation and therefore disrupt drilling, or the drill bit does in fact lodge itself within the formation and results in shutting down the well.
In the present state of the art, in order to prevent the possibility of a drill bit being lodged within the formation, there are numerous fluid which are pumped downhole in order to attempt to prevent such an eventuality, the most common being vegetable oil, mineral oil, and diesel oil as the base oils, in combination with emulsifiers and thinners (functional additives), as the lubricating combination, or the spotting fluid combination if in fact the bit has become lodged and must be dislodged.
Crude and refined oils were used as early as the 1920's to drill troublesome formations, free stuck pipe, and as completion and packer fluids. Later developments saw the use of No. 2 diesel oil as a common additive to mud systems. More recent environmental concerns over the toxicity of diesel oils required a base fluid change to less toxic refined mineral oils. Current industry requirements in offshore drilling are to have non-toxic fluids that can pass discharge guidelines as specified by the EPA Drilling Fluids Toxicity (reference).
Current oil based drilling fluid lubricants and spotting fluids are based on refined mineral oils and processed vegetable oils along with emulsification and dispersant additive packages.
Overall, these types of oils suffer from many drawbacks, the most pertinent being the fact that the oil is highly toxic to marine life. For example, should the oil in an offshore drilling operation spill over into the water, it has been determined that the mineral oil or vegetable oil, due to its heavy oily nature, will in effect coat the gills of marine animals and destroy valuable marine life. In fact, the Environmental Protection Agency has taken steps to assure that these types of oil are used under very stringent regulations during offshore drilling, and for the most part, in all likelihood should not be used at all. Vegetable oils have been used as substitutes offering a non-toxic alternative but have not proven to be effective performer in this application.